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Barium carbonate

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Conundrum

Fri Oct 04 2013, 05:38AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Hi all.
I recently acquired some barium carbonate and now have to test it for purity.
Also have some:- copper oxide, yttrium oxide and other assorted metal oxides.

Can any of you nice chemistry boffins suggest a way I might be able to test these
for iron and nickel content?
Apparently for HTSC less than 1 part in 10 exp 7 is the lower limit of working, ideally
99.99% purity of the starting materials is required for Y123 to work.

Re. synthesis, this isn't as bad as I thought as a workaround for the oxygen annealing
is to use a domestic microwave with an oxygen hookup to the quartz boat so it only
needs 1 hour calcination and 1 hour of O2 rather than the usual 36.
This can be done using any oxygen source from simple electrolysis in a U-tube to the
good old fashioned H2O2/MnO2 method.

I am able to send small amounts by post as long as they are less than 0.5 grams as
"research grade materials for analysis" , stored in a screw top container and securely wrapped.
Turns out that ceramics are permitted after all but you have to know who to ask

Bored Chemist

Sat Oct 05 2013, 03:35PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Sub ppm analysis isn't something you are likely to get working in a home lab unless you are prepared to put a lot of effort into it. Among other things, many reagents won't be that pure- for example if you dissolve the BaCO3 in acid as part of the analysis, you need acid with much less than 1 part Ni or Fe in 10^7.

It's almost certainly going to be better to send some to a lab for analysis.

What analytical equipment have you got?

Conundrum

Wed Oct 09 2013, 08:54PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Basic stuff such as microscope, oscilloscope, frequency counter. Might be able to kludge together a spectrometer using old webcam, tube and DVD segment as the prism to separate out the lines.

-A

Bored Chemist

Sat Oct 12 2013, 03:18PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Have you got plenty of time?
The big problem you have is that, unless you pay a lot for high purity reagents you could easily add traces of Ni and Fe to the material you are working with.
There is a potential way round that: add reagents as gases, Ni and Fe compounds are not usually volatile.
So, if you put some BaCO3 in a clean glass dish and put it in a closed container with another dish containing hydrochloric acid the acid will evaporate, condense on the BaCO3 and dissolve it to form a solution of BaCl2. You can't seal the container- the CO2 has to be able to escape. The sort of plastic container used to store food is probably a good choice. Use a clear one if you can.

OK, given time, that will give you a slightly acidic solution of BaCl2.

Take the dish of HCl out of the container and replace it with a dish containing ammonia solution.
That should get rid of any excess acid in the solution.
Then you need to produce H2S in the container by the reaction of dilute acid with a sulphide such as ferrous sulphide which can be obtained by the reaction of iron filings with powdered sulphur.. You need to make sure that no spray of droplets from the reaction can get to the BaCl2 solution- a plug of cotton wool in the neck of a bottle would probably do the trick.
If there's iron, lead, nickel or any of a lot of other "heavy metals" present in the BaCO3 then they will form a brown/ black precipitate when exposed to H2S.
It's a lot of trouble, it will be slow and it's not hugely sensitive but it would show up serious contamination by Fe or Ni.
I still think you should pay for an assay of it instead.

Steve Conner

Sat Oct 12 2013, 04:46PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

You could get it assayed, but wouldn't it be cheaper to just buy some barium carbonate etc of known purity from a supplier like Sigma Aldrich? It's not used for making drugs or bombs so there should be no issues.

Dr. Slack

Mon Oct 14 2013, 07:19AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

The first thing to do will be to do a dummy run, using none of the suspect material (so Fe content exactly zero), but all the other reagents and glassware you will need for the analysis. This does two things
a) a dry run for the analysis, might throw up somethings you hadn't thought of
b) analyses the residuals in your reagents and on your equipment, can you use shop HCl, or do you need the analar stuff that costs twice as much as the actual product? Are your cleaning procedures adequate?

Conundrum

Wed Nov 06 2013, 10:32AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

OK, thanks.
Do you have any suggestions on grinding?
I have a mortar and pestle, and have sulphuric acid for cleaning.

Maybe I should make an electronic mortar and pestle grinding device :)

Shrad

Wed Nov 06 2013, 10:05PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

a ball mill with mice balls inside a metal can that you can shut close with a plastic cover, and that you rotate using a laser printer paper roller on a motor

typical homemade ball mill

Conundrum

Thu Nov 07 2013, 06:06AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Thanks, will give this a try

EDIT: If anyone wants them I have 10g of Y2O3, BaCO3 and CuO ready to go.
I can adjust amounts of the last two if someone wants to make some 1-2-3 and
have some strontium carbonate on order as well.

Bored Chemist

Sat Nov 09 2013, 06:48PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

If you ball mill the stuff in a metal can, you don't need an analysis.
The iron content will be more than a few ppm.

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